Portable washing basin



FIG. 1 is a top front right side perspective of a portable washing basin showing my new design, the left side being a mirror thereof; and,

FIG. 2 is a bottom rear left side perspective thereof, the right side being a mirror thereof. The broken line showing is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a portable washing basin, as shown and described. 